Evaluation of the Use of Residual Materials from Bioconstruction Manufacturing as Soil Substrate Components

Abstract

In the construction sector advances are being made in the use of natural materials for the manufacture of new construction elements that are more environment- and health-friendly. Sub-products of vegetable origin derived from the manufacture of these materials may be used for other purposes in the industrial or agricultural sectors. Certain residues may even serve as crop substrate components to substitute peat, which is the most commonly used, non-renewable substrate. This study involves the physical and chemical characterization of three vegetable sub-products (pine bark, sunflower seed shells and hay made from ryegrass) generated at a company that manufactures construction materials using elements of vegetable origin, in order to evaluate their use as components of growing media. Testing indicated that none of these materials contained phytotoxic substances. The main physical characteristics included high porosity (>85%), high aeration (>30%) and low easily available water retention capacity (<20%) for the three materials studied. Pine bark was the poorest in nutrients (NPK, 0.19:0.01:0.11) and ryegrass hay presented the most adequate nutrient levels for substrate (NPK, 1.70:1.15:1.24). Twelve binary and ternary mixtures were prepared using these elements in different proportions as substrate to grow Tagetes patula in a greenhouse. Their growth was evaluated and compared with a commercially available universal substrate. The tested mixtures produced lower growth than the Control treatment, especially those containing more than 50% sunflower seed shells. The ternary mixtures interacted positively and their performance was higher than average. In order to be used as substrates, the physical properties of these materials should have been improved by mixing them with materials that reduce aeration and increase their nutrient content.